I work with children and I understand how they think and process information perfectly well. Nothing fazes me. Children are learning about themselves, others, and the world around them, which is all a lot to take in and understand. But they're working on it, from day one.
A chronological adult who never mastered the basics, on the other hand, baffles me. They aren't trying to understand anything, learn, grow, mature.. they somehow assume that everyone else should adapt to, and for, them. That kind of egocentric mentality makes sense in a child or even very early 20s, but it's ****ing weird to find in an adult. As good as I am with actual children, or interacting with people who have different issues in general.. the petty, selfish adult is beyond my skills or inclination to put up with.
I deal with those petty adults in a variety of ways, depending on how much I need to interact with them. Above all else though, I try to minimise my contact, as I've learned through bitter experience that l do not cope well with these people. You can't help someone who doesn't want help, they won't change unless they decide to change - and actually put in the hard work required to do so. Growing up is hard.
If someone made it to being a nominal adult without learning all those things one needs to know to be a functioning adult who can take care of themselves.. then they'll either have to do the hard work later, or (more likely, I'm afraid) spend their life relying on others to carry them. Not support. Carry. Every single time the hit the limit of their mental and/or emotional maturity, other people will be expected to step up and work things out. No matter how obvious it may be to everyone, this person will ignore all advice, all offers of help, and just drift along til the next crisis.
And they *love* drama. Things are dreadful or they are wonderful. You are their close, trusted friend or an enemy. Where this makes complete sense in a child, as the brain forms deeper understanding of complex human behaviours... in an adult, it's a clear sign they need help ASAP. And to be far, far away from me in the interim. This includes family members.